diff options
| author | Anup Patel <anup.patel@wdc.com> | 2020-09-17 15:37:10 -0700 |
|---|---|---|
| committer | Palmer Dabbelt <palmerdabbelt@google.com> | 2020-10-02 14:30:57 -0700 |
| commit | 8f3a2b4a96dc014e99e1df327db1450fdbbd5e15 (patch) | |
| tree | 5d1bcde041ee3609ec8e1e7081cbd76bf5574f32 /arch/riscv/kernel/setup.c | |
| parent | 8a3f30c4319dc70547f11c18da2e7b5987543aa1 (diff) | |
| download | lwn-8f3a2b4a96dc014e99e1df327db1450fdbbd5e15.tar.gz lwn-8f3a2b4a96dc014e99e1df327db1450fdbbd5e15.zip | |
RISC-V: Move DT mapping outof fixmap
Currently, RISC-V reserves 1MB of fixmap memory for device tree. However,
it maps only single PMD (2MB) space for fixmap which leaves only < 1MB space
left for other kernel features such as early ioremap which requires fixmap
as well. The fixmap size can be increased by another 2MB but it brings
additional complexity and changes the virtual memory layout as well.
If we require some additional feature requiring fixmap again, it has to be
moved again.
Technically, DT doesn't need a fixmap as the memory occupied by the DT is
only used during boot. That's why, We map device tree in early page table
using two consecutive PGD mappings at lower addresses (< PAGE_OFFSET).
This frees lot of space in fixmap and also makes maximum supported
device tree size supported as PGDIR_SIZE. Thus, init memory section can be used
for the same purpose as well. This simplifies fixmap implementation.
Signed-off-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Diffstat (limited to 'arch/riscv/kernel/setup.c')
| -rw-r--r-- | arch/riscv/kernel/setup.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c index 2c6dd329312b..edea7ef88402 100644 --- a/arch/riscv/kernel/setup.c +++ b/arch/riscv/kernel/setup.c @@ -48,8 +48,9 @@ atomic_t hart_lottery __section(.sdata); unsigned long boot_cpu_hartid; static DEFINE_PER_CPU(struct cpu, cpu_devices); -void __init parse_dtb(void) +static void __init parse_dtb(void) { + /* Early scan of device tree from init memory */ if (early_init_dt_scan(dtb_early_va)) return; @@ -62,6 +63,7 @@ void __init parse_dtb(void) void __init setup_arch(char **cmdline_p) { + parse_dtb(); init_mm.start_code = (unsigned long) _stext; init_mm.end_code = (unsigned long) _etext; init_mm.end_data = (unsigned long) _edata; @@ -76,7 +78,10 @@ void __init setup_arch(char **cmdline_p) #if IS_ENABLED(CONFIG_BUILTIN_DTB) unflatten_and_copy_device_tree(); #else - unflatten_device_tree(); + if (early_init_dt_verify(__va(dtb_early_pa))) + unflatten_device_tree(); + else + pr_err("No DTB found in kernel mappings\n"); #endif #ifdef CONFIG_SWIOTLB |